Cantonese or Yue is a major dialect group or language of the Chinese language, a member of the Sino-Tibetan family of languages. Cantonese is spoken by 71 million people. The area with the highest concentration are in Guangdong and some parts of Guangxi in southern mainland China, Hong Kong and Macau. Other major groups include Chinese minorities in Southeast Asia and by many overseas Chinese of Guangdong and Hong Kong origin worldwide. The name is derived from Canton, a former romanized Western name for Guangdong.

Different dialects of Cantonese exist, the most widely spoken is the Guangzhou dialect, also referred to simply as "Cantonese". The Guangzhou dialect is the lingua franca of not just Guangdong province, but also the overseas Cantonese speaking diaspora. The Guangzhou dialect is also spoken in Hong Kong, one of the financial and cultural centres of China. In addition to the Guangzhou dialect, the Taishan dialect, one of the sei yap or siyi dialects that come from Guangdong counties from whence a majority of Exclusion-era Cantonese-Chinese immigrants emigrated, continues to be spoken both by recent immigrants from Taishan and even by third-generation Chinese Americans of Cantonese ancestry alike.

Like other major varieties of Chinese, Cantonese is often considered a dialect of a single Chinese language for cultural or nationalistic reasons, though in practice Cantonese, like many other Chinese language varieties, is mutually unintelligble with many other Chinese "dialects".

Cantonese is spoken by about 66 million people mainly in the south east of China, particularly in Hong Kong, Macau, Guangdong, Guangxi and Hainan. It is also spoken in Malaysia, Indonesia, Thailand, Singapore, Philippines and among Overseas Chinese communities in many other countries.

In many schools in Hong Kong and Macau, Cantonese is the medium of instruction, though the students are taught to read and write standard Chinese, which they read with Cantonese pronunciation. Cantonese is also the main language of business, the media and government in both Hong Kong and Macau.

Cantonese has appeared in writing since the 19th century. It is used mainly in personal correspondence, diaries, comics, poetry, advertising, popular newspapers, magazines and to some extent in literature. There are two standard ways of written Cantonese: a formal version and a colloquial version. The formal version is quite different from spoken Cantonese but very similiar to Standard Chinese and can be understood by Mandarin speakers without too much difficulty. The colloquial version is much closer to spoken Cantonese and largely unintelligible to Mandarin speakers.

In Hong Kong, colloquial Cantonese is written with a mixture of standard Chinese characters and over a thousand extra characters invented specifically for Cantonese. The extra characters are included in the Hong Kong Supplementary Characters Set (HKSCS).